Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
  • B01D3/14—Fractional distillation or use of a fractionation or rectification column
  • B01D3/32—Other features of fractionating columns ; Constructional details of fractionating columns not provided for in groups B01D3/16 - B01D3/30
  • B01D3/322—Reboiler specifications
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
  • B01D3/001—Processes specially adapted for distillation or rectification of fermented solutions
  • B01D3/003—Rectification of spirit
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
  • B01D3/34—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping with one or more auxiliary substances
  • B01D3/40—Extractive distillation

Definitions

• the present invention concerns a method for the purification of a two-component liquid mixture by distillation, in which method the liquid mixture to be purified is supplied into a multi-plate purifying column, between its bottom space and still head, a diluting liquid consisting of one of the components of the liquid mixture is fed into the column, a distillate containing volatile impurities is obtained from the still head and the purified two-component liquid mixture is obtained from the bottom of the column.
• the invention also concerns a distillation apparatus for the purification of a two-component liquid mixture by distillation, said apparatus comprising a multi-plate purifying column; feed equipment for supply ⁇ ing the mixture to be purified into the column below the top plate; feed equipment for supplying a diluting liquid consisting of one of the components of the liquid mixture into the column; a still head outlet, with possible refluxing, for the removal of the distillate vapours from the still head; and a bottom outlet, with possible refluxing, for the removal of the bottom product from the bottom of the column.
• the invention relates to a meth ⁇ od and an apparatus for the purification of a two-compo ⁇ nent liquid mixture by distillation, said two-component liquid mixture containing a compound with a higher boil- ing point and another compound with a lower boiling point.
• These compounds of the liquid mixture may be any liquids permitting purification by distillation.
• the invention concerns a method and a cor ⁇ responding apparatus for the purification of a mixture of water and ethanol in the manufacture of drinkable alcohol.
• the alcohol is usually separated by distillation in a mash column in which raw alcohol is obtained from the still head and the grain with low alcohol content from the bottom.
• the raw alcohol obtained from the mash column usually having an alcohol concentration of 30 - 50 % by weight, can be passed to a purifying or hydroselection column either directly in the vaporized state or in liquid state after condensation, or after it has been rectified into raw spirit, which typically has a concentration of 88 - 94 % by weight.
• the raw alcohol or raw spirit is diluted with water and subjected to extractive distillation. During this stage, the raw alcohol is effectively purified of substances that are undesirable in clear spirit of neutral smell and taste, e.g. vodka.
• the evaporability of the impurities increases as the ethanol content of the water-ethanol mixture decreases.
• the rest of the impurities contained in the ethanol- water mixture obtained from the bottom of the purifying column are concentrated partly in the still head and partly in the so-called fusel zone of the rectifying column, from where they can be removed.
• the fusel zone of the rectifying column is located in the region where the ethanol content of the ethanol-water mixture boiling on the column plates is approx. 10 - 70 % by weight.
• a so-called methanol column is used. From this, the pure alcohol is obtained from the bottom while the fraction containing impurities, e.g. methanol, is obtained from the still head.
• industrial extractive purifica- tion of raw alcohol can be implemented in two ways re ⁇ garding the manner in which the diluting water is sup ⁇ plied into the column.
• the raw alco ⁇ hol and the required diluting water are fed in together onto the same plate, located several plates below the still head.
• the purified ethanol-water mixture typical ⁇ ly having a concentration of 8-20 % by weight, is ob ⁇ tained from the bottom of the column while the undesir ⁇ able compounds are removed from the still head in the form of distillate vapour.
• the ethanol content of the dis- tillate vapour obtained from the still head typically amounts to a value exceeding 80 % by weight.
• the raw alcohol is fed into the column at a point below the top plate while the diluting water is supplied onto the top plate of the column.
• the purified ethanol-water mixture typically having a concentration of 8-20 % by weight, is obtained from the bottom of the column.
• the undesirable compounds are re ⁇ moved from the still head of the purifying column in the form of a distillate vapour which typically has an ethanol concentration below 30 % by weight.
• the distillate vapour obtained from the still head need not be refluxed after condensation back to the top plate, because the diluting water supplied to the top plate constitutes a reflux in the upper part of the column and is responsible for the low ethanol content of the distillate vapour obtained from the still head.
• the liquid is heated to a boiling temperature by means of steam either directly by supplying it into the bottom space of the column or indirectly using a heat exchanger.
• the purifying column typically needs 1 - 3
• the object of the invention is to achieve a method and an apparatus for implementing purifiying distillation in such a way as to reduce the energy required for the distillation to a level essentially below the energy requirement of previously known methods and apparatuses.
• the present invention provides a new and sur ⁇ prising solution regarding the energy requirement of the purifying column.
• the heat content of the vapour obtained from the still head of the purifying column can be utilized for the heating of the bottom space of the same column.
• the vapour obtained from the still head of the purifying column need not be compressed mechanically or by other means to increase its temperature.
• the mixture itself or one of its compo- nents e.g. the one with the lower boiling point
• the other component e.g. a diluting liquid having a higher boiling point
• the supply of the diluting liquid and the operational conditions in the column are adjusted as described below so as to ensure that the temperature in the still head is higher than the temperature at the bottom of the column.
• the vapour obtained from the still head can be used for the heating of the bottom space.
• the apparatus of the invention comprises equip ⁇ ment for supplying a diluting liquid onto the top plate, below the top plate or both onto and below the top plate, and equipment for supplying the liquid mixture to be purified into the purifying column at a point below the point of supply of the diluting liquid.
• the novelty in the apparatus of the invention is its equipment for passing part of the heat content of the distillate vapour obtained from the still head into the bottom space of the column e.g. by means of a heat exchanger serving to maintain a boiling temperature in the bottom space.
• the boiling tem ⁇ perature of the liquid at the bottom was always dis ⁇ tinctly higher than the temperature of the distillate vapour obtained from the top of the column because the liquid at the bottom has a lower ethanol content and a higher pressure than the distillate vapour obtained from the top.
• the second operational mode of the purifying column by varying the amount of diluting liquid used, the position of the point of supply of raw alcohol in the column and the intensity of the boiling, it is possible to exert a strong influence on the temperature of the distillate vapour removed from the top of the column and, to a lesser extent, on the boiling point of the liquid at the bottom of the column.
• the purifying column has 25 - 50 bubble, sieve or valve plates, across which the pressure loss in the column during distillation is usually 75 - 250 mbar. If packed column fillers with a small pressure loss are used, the pressure difference in the column can be kept at a level below 50 mbar.
• the distillate vapour obtained from the still head of the purifying column is passed essentially as such and directly from the still head to the secondary side of a heat exchanger communicating with the bottom space of the same column, in such manner that the distillate vapour is partly or completely condensed in the exchanger, which transfers the condensation energy of the vapour to the bottom space for use in the boiling of the liquid.
• the arrangement provided by the invention makes it possible to achieve a substantial reduction in the amount of external energy required by the purifying column.
• the apparatus of the invention can also be used for the purifying distillation of raw alcohol or impure spirit produced in other ways besides fermentation, e.g. synthetic spirit.
• the alcohol to be purified has a concentration of e.g. 20 - 90 % by weight.
• the alcohol to be purified is raw alcohol obtained from a mash column and has a concentration of 35 - 50 % by weight.
• the alco ⁇ hol to be purified is raw alcohol with a concentration of e.g. 88 - 94 % by weight.
• the method and apparatus of the invention are also applicable for the purification of other liquid pairs besides water-ethanol mixtures.
• Such liquid pairs may consist e.g. of water and other kinds of alcohol, water and other organic liquids, and/or organic liquids in general.
• Fig. 1 presents a flow- chart illustrating the operation of an industrial-scale distillation apparatus representing the state of the art.
• Fig. 2 presents a flow chart representing an embodiment of the method and apparatus of the invention.
• Example 1
• a purifying column as illus- trated by Fig. 1 was used.
• the column was a 45-plate bubble plate column.
• Raw alcohol e.g. the distillate obtained from a mash column
• the raw alcohol feed can be preheated in some other heat exchanger belonging to the distillation system.
• the purified weak alcohol solution typically having an ethanol content of 8 - 20 % by weight, was passed from the bottom space 6 via output line 7 to other parts of the distillation system for further processing.
• the ethanol-containing vapour obtained from the still head 5 of the purifying column is passed via line 4 into a heat exchanger 12, where it is condensed.
• the condensed vapour, the so-called distillate was removed from the heat exchanger via line 10 and directed to other parts of the distillation system for further processing.
• the apparatus was provided with another heat exchanger 8 connected to the bottom space of the column. Via line 10, primary vapour was supplied to the primary side of the heat exchanger.
• the condensed vapour, the so-called primary condensate was removed from the heat exchanger via exhaust line 11 and passed to other parts of the distillation system for further processing.
• the heat energy released in the condensation of the primary vapour was transferred to the secondary side of the heat exchanger and further via line 9 to the bottom space of the purifying column, causing the liquid in the bottom space to boil.
• thermal power fed into heat exchanger 8 in example 1 can be calculated as follows:
• the distillate vapour flow 4 Since the distillate vapour flow 4 has an etha ⁇ nol content of 2.64 % by weight, the temperature falls in the total condensation from 105°C to 101.9"C. Since the condensation temperature in the total condensation is higher than the temperature in the bottom space of the purifying column in example 1, the distillate vapour can be directed to a heat exchanger providing heat for the boiling of the liquid in the bottom space as illus ⁇ trated by Fig. 2, thus enabling the entire condensation heat to be transferred to the bottom space to maintain the boiling temperature.
• Example 2 shows that the method and apparatus of the invention enable the required external boiling energy of the purifying column to be reduced from a value of 2627 MJ/h to a value of 200 MJ/h.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=8527655

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Country Status (4)

Cited By (71)

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• 1988
  • 1988-12-30 FI FI886052A patent/FI80218C/fi not_active IP Right Cessation
• 1990
  • 1990-01-02 AU AU48223/90A patent/AU4822390A/en not_active Abandoned
  • 1990-01-02 WO PCT/FI1990/000002 patent/WO1990007367A1/en not_active Application Discontinuation
  • 1990-01-02 EP EP19900901597 patent/EP0456647A1/en not_active Withdrawn

Non-Patent Citations (1)

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